Indicating instrument deactivation indication apparatus



DE .GIERS INDICATION APPARATUS Flled June 28 1946 INDICATING INSTRUMENT DEACTIVATION June 13, 1950 INVENTOR. CLARENCE/117E G/ERS A TTOENE'Y Patented June 13, 1950 UNITED :S TATES INDIGATING INSTRUMENT 'DEAC'TIVAI EION INDICATION APPARATUS Clarence A. de Giers, ForestHills,.N.Y., assignor to The Liquidometer Corporatiom'L'ong' Island City, "N. Y., a corporation of'Delaware ApplicationJune 28, 1946, Serial.-No.;67 9,921

SClaims. (Cl. 171 95) instruments, which are activated by the flow-of electric current therethrough, and wherein it is desired to indicate to an observer that for some .reason the flow of current has ceased, so that the instrumentdoes not record or indicate the -.true magnitude of a condition, which it is designed to indicate when activated in the usual way. Theinvention is not, however, specifically limited to electrical instruments, nor to instru- -.ments for indicating any particular condition, and is applicable to instruments which may in- :dicate the magnitude of any condition, positive .-or. negative, and chemical, physical or electrical character. Electrical instrumentsoften have embodiedv in their construction provision for returning the pointers to some"off position when the instrument is not in use. Suchprovisions are impor- ..-tant .in, practice, since in. the event of .power failure, they will cause the pointer to swing to nsome predetermined point, as off-scale, thereby gwarningthe operator that the system has been shut downjdeliber-ately or has failed inadvert- -ent1y,-:and.-thus preventing him from obtaining aerroneous readings. 'In somev instruments, such ratiometers, these provisions have included the introduction either .of hair springsor of stationarily mounted, permanent-auxiliary .magzrnets. Suchdevices, however, have the. disadlvantage that they introduce a constant force -eifectivenpon themotionand hence the posi- .-tion-. of the pointer or mov'able indicating element throughout the use of the instrument. While such errors-may sometimes be calibrated out of the-instrumentmy adjustment thereof or by suitable permanent variations in the. scale graduations, Tthe tneverthelesscause scale dis- 'tortion,- which results in some non-linearity in respectto a-normalescale. Furthermore, when considering the efiect-ofvoltage fluctuations on .aanindicator 'suchzas-a ratiometer, it has been remains. substantially. constant throughout, the entire range of voltage.fluctuations, this}latter force, being no longer proportionalorfdeterminable in respect to the force,effeotivefto'position the movable element of the indicator, introduces an error into the indication.

Other methods. of indicating .powelffailure have been the employment ,of.,,oneorfmore'jpilot lamps. This method has been found inotlcompletely reliable, since it. is fpossiblefforithe' ,lamp

itself toffail, thus, limiting its, utility.

Another limitation jin. the .use OfJStatiOnariIy mounted, auxiliary permanent magnetsisthat in long scale indicators, such as'tho'seih'a'ving approximately 360 scales, there is usually a dead spot at which the effect of the auxiliary permanent magnet is neutralized. In "such a construction, if the, power isturned off iorf fails when" the pointer" or movable indicating element is approximately directly opposite "the fpower off position, it will'fa'ilito returntosuchposP tion "due to the forces. tending to "move it'inj'opposite"directions' being equal. As a result, if the movable indicating element happensitdibejjin' the dead zone at the time of power Cut-611 orifail- ,ure, it may remain in that jpositio'nygiving an strument having a permanent magnet movable --:-sincee thes effect-.01 the pointer returning means with the movable indicating element, an auxiliary magnet mountedfor movement into and out of the field of the first named permanent magnet, so that when the power is on to the instrument, the auxiliary magnet is maintained wholly outside the field oi the first named permanent magnet and does not affect the position of the pointer or other movable indicating element. "In this way the auxiliary magnet will not introduce'errors into the indication provided by the instrument in the event of voltage fluctuations and at the same time will not afiect or require achange in the normal scale calibration of the instrument.

-A further object of the invention is to provide a path of movement for the auxiliary magnet between its inoperative position and its operative position, such that, in the event that the power is cut oil or fails at a time when the movable indicating element is in the dead zone, as above set forth, a force will be brought into effect during the movement of the auxiliary magnet to its operative position, to move the movable indicating element out of the dead zone position so that this element will be insured of movement to the predetermined off-scale position indicating that the instrument is deactivated.

A further object of the invention is to provide a means for moving a pointer or other movable indicating element of an instrument as aforesaid to a predetermined position indicating deactivation of the instrument without employing an additional power source other than that required for the normal operation of the instrument.

Other and more specific objects of the present invention will become apparent from the following specification and appended claims, When considered in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic illustration showing an electrical instrument having means for indicating deactivation of the instrument in accordance with the present invention; and

Fig. Zis a, fragmentary view of an instrument embodying the present invention taken substantially on the line 2-2 of Fig. 1, but showing the pointer at the predetermined oil-scale position corresponding to that shown in dotted lines in V Fig. 1.

' barometer, the barometric capsule, which is responsive to the surrounding barometric pressure,

is usually constantly mechanically connected to the pointer of the instrument. In such a case, there is no call for an apparatus by which to in dicate when the instrument is out of operation, r

for, due to the continuously operating mechanical connection between the actuating means and the indicator, the instrument is always actuated orenergized.

On the other hand, the invention is applicable to any type of indicating instrument, which may be activated or de-activated either manually and deliberately, or, for example, by the failure of some part or the opening of an electrical circuit and inadvertently. Under such circumstances it is important to know that the instrument is out of operation, the indication of which condition is a major purpose of the present invention.

The invention is applicable to instruments whether mechanically or electrically operated or operated by some combination of both mechanlcal and electrical means. The actuation of the movable indicating element in accordance with the present invention may be effected mechanically or by some mechanical and/or electrical interconnection, and means (mechanical or electrical in character, or both) may be provided according to the present teaching to set the mov- 'able' indicating element to a position indicating that the instrument is out of operation or deactivated. As such, the reset means, which particularly forms the subject matter of the present invention, may be mechanical or electrical, or as hereinafter specifically disclosed, a combination of both. It may also be applicable to instru-- ments wherein the indication is effected b the relative movement of any two parts. For example, in the instrument particularly hereinafter described, a pointer is made rotatable with respect to a fixed scale. Thus the pointer is the movable indicating element and the scale, the fixed indicating element. Such elements could be in effect interchanged, for example as a, compass card, to put the scale on the movable element and to use a single, fixed index cooperating therewith. Again, while the relative motion in the present case as particularly hereinafter described is circular, i. e., about 9, single axis of rotation, it is contemplated that the invention could advantageously be applied to instruments wherein the movable element operates in a straight or otherwise shaped path.

Considering now the application of the invention to an electrical instrument, and wherein the instrument itself, such as the ratiometer hereinafter particularly described, employs permanently magnetized armature or rotor parts as a part of the instrument per se, the reset arrangement may be effected by the introduction into a magnetic field of a permanent magnet of the rotor of a directional magnetic force which will react with the field of this permanent magnet of the instrument to cause a movement of the indicating element thereof to a predetermined 01T- scale position. This may be eiTected as particularly hereinafter described b moving a magnet between an operative position in the field of this instrument magnet and an inoperative position out of this field or by providing an electromagnet stationarily located, in this field and energized only when it is desired to move the instrument to its off-scale position, i. e., when the instrument as a Whole is deactivated. On the other hand, in the event that a movable, auxiliary, or reset magnet is used, it may be either a permanent magnet or an electromagnet, energized at least at the proper times, if not continuously. The following description and appended claims are to be understood with these principles and requirements in mind.

Referring now to the accompanying drawings and particularly to Fig. 1, there isshown at H), an indicator or indicating instrument of the ratiometer type, which is shown cooperating with a telemetering type transmitter H, these instruments being indicated as entities by the dotted outlines shown on the drawing, Fig. 1. Also, for purposes of illustration, the transmitter H is shown applied to the measurement of the liquid level in a tank I2, which may, for example, be the fuel tank of a motor vehicle or an airplane. The transmitter H may comprise an electrical resistance element I3, which may be divided into three sections by, taps l4 and 15. A wiper I6 is arranged to move over the resistance element l3 in any suitable way as by the action of a pulley I1, a float 18 in the liquid in the tank I2 and a counterweight 19. As shown, a, suitable flexible element such as a rope, cord or chain 20 is trained around the pulley I1 and. connects the float l3 and the counterweight 19. Thus, when the float I8 is at the bottom of the tank, the wiper It will be at the left handend (as'shown, Fig. '1) of its movement in respect to the resistance element 13, When liquid is iilled into the tank l2, so that the level gradually rises, the

agerness '5 "'16 will inove correspondingly toward the arm es, which is siiitably pivoted as n'd end (asshoWh) of its mOVernenVi-n '--Ina-tical1-y illiistrate'd ih IF"ig.}1, 'for "mbv "respect to 'theresistance element i3. ab'o'ut 'a fixed1boi-i'it' GL -So that it 'may inoye be- The indicating instrument IE) shown on the tw en an mopratiye position shown in full lines accompanying"drawings rnay be of the rati- 5 "atftherigh't-in Fig; 1, through an 'interinediate ometer type such, for example, as is more parposit-ion indicated by the refern'cenh'mbe'r 62 m impending jointappli- -"th'at figure *Whrei-n the parts ---"ar e slfo'w n in 'ppli'cant-and Osterlund, "brokenlines, to an op rative position substan- I v I I I "tiall-y centrally or the instrument lily-as musthofizi'sofsel,"trained $eptember28, fi' tratedin broken-lines at 63 andalso snown ni full lines' 'in Fig. 2. ---'At the operative position, v "themagne't 58-will be in the-fie1dof at least one g mtenddaslin'ii'fiing thep'resent invention. of-the permanent magnets carried by the r'otor instrument fcoiniirises "three perm nently "ii ifas shown, i. e.,' within -the field of the-magnet oils"2i 22, 2'3, Whi'ch are spaced about a -1 shown particularly in Fig. 2 at 26.

" g errtto eenera11 indicated at When the indicating instrument is die-ener- Fig. Zoffthedrawings-theme? ized as by cessation of electric curr'ent' flow rotor include two similar hiug-h -the coils 2'l,---2-2 and 23, the permanent ets 2' a'n'dflfi; spaced-apart on a magnet 55 is-s'v'vung 'to the positiontt '(Fig; -1 o'n' rotor. haft"2"i,-Which-is suitably 'jourf by a 'spnn ti which'is'conncted to-extend beai brof' ia t yh sb ings in the instru- "tweenap'oint on the arm 59,*ShOWn'at- -GSJ-afid ehiagnets z'liandfitb'eingadaptedto be a fixed anchorage 66. A suitable stop 61 1s" pros acedfrbnibutto' overlieand underlie,-respec- -Vided tolimit the niovementof the arm GU -in a thed'isc 'liiie'coils 25,22 and2'3,-tWo'-0f clocktvisedirection frbin the full line (inopera- I area wirinFigr-l Thep'ermanent 'magg tiye) position shown toward its operativepo'siand i'fiare bfeferablyof some material tionsh'ownat 53, Fig. 1. At the-position 63;--the highi-etentiyity, suchaisAlnico, and'arepref- -permanent maght-iflis in the field-'of-thdifleieiabi'y"hfouiited 'coaxiaiiywiththe shaft "2! 0f "net Ziiftltereof -ahd"'Wii1 affect i-ts"pOSitioneJrld he "rotor. Also secured -to"'the shaft '21 is a "hence that-of "the "movable indicating-element inter fifwhic'h isthe movableindicating=eleg iii. The au xiliary Iiiagnet 5B -is preferably arm eiitjoftheinstruine'nt shown, this element co- -"ranged to move-mew the rotor ze as b'est shown ating witha'stationary scaieorflxed indi'catin "Fig 2.

eiein'ehthereshowndiagrammatically in Fig. Also" soop"eratin'g withthe auxiliary magnet 58 2 h b hwassficiated thereand the am 66 by which" it is carriedand forthe ththreeieittois or magnet-coils ti andefgg p po t bv n itm gr a di 'agn t tofitheir 2,"vvhi'ch""tvill be described hereinafter in furinoperative position is asolen'oid"or electromag- "tfiendetail. The lower-mag e 0 3 is shown netic holding means "generally indicated at 68, f n'Fi'g. 1 as itisthe 'fleldof thismagnet whic iiihich' m ay be "of anysuit'able type, but-is sho'tt'n 'inplC fi g'" Ofthfi pointer as I *as-be'ing made i-i'pwith a castiron core Sa on iihafter-set forth. lowhich'are Wound-the resistcrs su, 3| and 32. I The aforesaid arts'are electrically connected The mag'netic circuit is then completed through liysuitable boniiuct'o'rs as follows. One emit? *a heel p'ie"ce 70 and a clapper or armature 1|, of the resistor 39 is connected to an end -34 of *w'hich is hinged -tothe heel'piec'e 7B ata point c0i 1 2 3 "and'a'lso to'the e d 3 a 3% 0f the 12. When the's'olenoid is energized, the clapper mitterresistor it by'line Wires 3'! and 3B.=i5 5"or armature -Hisp'u1led against the'c'ore 69*as 9" is connected to one shown infull lin'es in-Fig; 1 and in so doing acts d Zt i]-'"of -tl1e-coil'-2l andalso t0 the p 0f 5 through a co'nn'ectio'n it to overcome'the tension he transmitter resistance element it by line -of*the -spring"64, thereby swing'ingthe armature res- 41 ana -a2. "Similarly One end 3 0f the 651 in-a counterclockwise direction, as shown in 9 32 isicbninected'to one end M of the iio' hig. 1; to the fullline position thereof as shown aiidjalsj'o 'to't t p transmitter 'in that figure at which the magnet'58 is laterally j me'nt- 'iebyline-wires ae'and'tt. The three inner b t of t fi 1d of t r t gnet d hds'"'fi 'l'," i8and" ieof the coils-2i, 22 and-23,'re- "sired, means -(n'ot shown) 'may be provided-for ectiyly'iare conn d h r y a mm n shielding the permanent magnet 59 at its inop- "Efl ""Si lnilal'riyrthe t r remaining ds wi 5 "eratiyeposition. Such an arrangement may be rid 53 ofthere' isfiors 3%, 3 and 3 are made of importance where space limitations are critimrnon, and connected-tonne terminal of a cal. "Furthen if desired, the connection between switc fi y 'a li'hewire 55. The other terminal 'the-cIapper Tl and 'the'p'oint tfi as shown may-be f w chhfi "is connected toone (the posieither a resilient connection including a spring )'terminal ot"ab t ery 5%, 01" other 501111361130 14' or may bea non-resilient and/or an inflexible irect 'current'E. M. F tne other (negative) *ii-nkty'pe connection. 7 t rmin'al-of whichis connected through a line While the resistors-3t,- Stand 32 may bea' part irefimito w l The wn'itruction O "of'the indicator circuit'as shown, it isp'refe'rred he in trumentystem as thus far described in to'use the power consumed by these resistors to pecttoFigs. 1 and 2 may be considered subifect'the movement of the arm 60 and the auxtantially {the same-as that of application Ser. iliary permanent magnet 58 to their inoperative No 3300 aboyereferred to, the operation of positionby energizingthe solenoid 68. Forthis vir'h hwill'beobvious to those killed in'the r purpose, these resistors are Wound as coils about "accordance with the present invention, an the core 69 so that all of them, whenenergized, uxiliary permanent magnet 53 is provided to 70 tend to draw the armature or clapper H toward rig the pointer 28 to an oif-scale position, the core 69 from the dotted line position tothe uch' 'as-th at shown in dotted lines at 59 (Fig. 1) full line position of'the parts shown. In this'way "lien'thepowerito the coils 25, 22 and-23 is oii, the operation of the auxiliary magnet may be exampleby the opening of the switch 5 obtained without-anyadditional power-consumpwho'au'i'cili'ary"magrnet mounted rigidly on an tion. Furthermore; *tvh-il-e for the ei-rcuit shown the-yoltage across the coils 2|, 22 and 23, and hence alsothatacross coils 3Q, SI and 32,- may invention, the instrument disclosed here will be substantially independent of line voltage fluctuations, as these disturbing influences are removed 'by the use of the present invention. Also, since the return magnet 58 is moved to and held in an inoperative position during the normal operation of the indicator, this magnet will not affect the normal scale characteristics of the indicating element.

t is also contemplated that the return magnet could be permanently positioned at the position shown at 63 in Fig. 1 and shown in full lines in Fig. 2, and take the form of an electromagnet,

current through which from a suitable source of direct current E. M. F., in order to make the magnetic force created thereby directional in character, could then be controlled by a relay switch from the same or some other source of E. M. F. as the main instrument circuit, i. e., the battery 56; and a relay switch provided operated by a solenoid as shown at ill, the arrangement being such that when the relay was de-energized, the switch would be closed, and vice versa.

Referring now to Fig. 1, the manner in which the present invention provides for the elimination of the dead spot from which the pointer of previous instruments would not return to an offscale position, substantially 180 distant therefrom, will now be described in greater detail. As previously stated, indicators of the prior art had difiiculty under these circumstances when the pointer was at about 180 from the preferred offscale position at the time power was cut ofi. This was partially due to the equal repulsion of the poles of the rotor magnet and the return magnet and partially to such friction as might exist in respect to the moving element. According to the present invention, this condition is effectually eliminated by causing the auxiliary magnet en route from its inoperative to its operative position to swing in from the side'as shown. Assuming, for example that the power is cut off as by opening the switch 54 when the pointer is indicating a mid-scale position as shown for example in Fig. 1 in full lines, then as the auxiliary magnet 58 moves toward its operative position and passes through the intermediate position shown at 52, Fig. 1, the reaction between the north pole of the auxiliary magnet and the south pole of the rotor magnet 26, will impart a spinning force to the rotor sufficient at least to move it from the dead spot position. When the auxiliary magnet thereafter comes to its full operative position shown at 63 in Fig. 1 and in full lines in Fig. 2, it will be efiective to continue the movement of the rotor to the position'of the pointer shown in dotted lines at 59 in Fig. 1, which is the predetermined elf-scale position of the present invention as shown in the'drawings.

While there has been shown and particularly described herein but one specific embodiment of the invention, the range of equivalents and the requisites for such equivalents have been particularly' pointed out hereinabove and are further pointed out in detail in the appended claims which are to be construed validly as broadly as the state of the prior art permits.

What is claimed is:

1. In an electrical indicating instrument having a movable indicating element cooperating with a fixed indicating element for indicating the magnitude of a condition and means including a plurality of coils, through which current may be passed, constructed and arranged to be activated and deactivated by the passage and cessation of current through such coils and effective when activated for positioning said element to indicate said magnitude, apparatus for moving said movable element to a predetermined position to indicate that the instrument is not operating, comprising means movable between operative and inoperative positions and when at its inoperative position electrically and mechanically separate and distinct from said element moving means and as to which the position of said movable element is independent during the activation and consequent operation of said element moving means, an electromagnetic holding means having a plurality of windings which are respectively in the circuit with each of said coils and are all operated in response to flow of current therethrough for holding said movable means in its inoperative position during all the time in which said movable element is positioned by said element moving means in accordance with the magnitude of the condition to be indicated, means efiective to move said movable means to its operative position upon the cessation of current fiow through all said coils and the consequent cessation of current flow through all the windings of said electromagnetic holding means, and means operating in response to said movable means moving to its operative position for moving said movable element to its predetermined position aforesaid.

2. In an electrical indicating instrument having a movable indicating element cooperating with a fixed indicating element for indicating the magnitude of a condition and means including a permanent magnet movable with said movable element and a plurality of fixed coils magnetically associated therewith and constructed and arranged to be activated and deactivated by flow and cessation of current through said coils respectively and effective when activated for moving said movable element to indicate said magnitude, apparatus for moving said movable element to a predetermined position to indicate that the instrument is not operating, comprising means separate and distinct from said movable element and parts moving therewith and as to which the position of said movable element is independent during the activation and consequent operation of said element moving means for interposing in the field of said permanent magnet, only during the deactivation of said element moving means, a directional magnetic field capable of reacting with the field of the first named permanent magnet to move said movable element to a predetermined position aforesaid, and means including an electromagnetic holding means having a winding in the circuit with each of said coils respectively for controlling the effectiveness of said directional magnetic field so as to restrict its eiiectiveness to time periods during which said electromagnetic holding means is de-energized by the cessation of current flow 9; through all the windings -thereof due to-cessation oi current flow-through allof: said coils.

3. In an: electrical indicating instrument hav-. ing; a movable indicating; element: cooperating with a fixed 'indicating elementforindicatingthe magnitude of a condition and means including a permanent magnet" mounted tomovewithsaid for moving said movable element:-toiindicateisaid magnitude; apparatusfor -moving saidmovable element to a predetermined position to indicate thatthe, instrument is nOtpperating, comprising means, including a second permanent magnet movable between operative and inoperative positions and when at its operative position electrically and mechanically separate and distinct from said element moving means, said second permanent magnet When at its inoperative position being substantially outside the field of the first named permanent magnet, and as to which the position of said movable element is independent during the activation and consequent operation of said element moving means, an electro magnetic holding means having windings respectively in circuit with each of said coils and operated in response to the activation of said element moving means by the flow of current through any of said coils for holding the second named permanent magnet in its inoperative position out of the field of the first named permanent magnet during all the time in which said movable element is positioned by said element moving means in accordance with the magnitude of the condition to be indicated, means effective to move said movable means and said second named permanent magnet to its operative position upon the deactivation of said element moving means and consequent de-energization of said electromagnetic holding means by cessation of flow of current through all the windings thereof, and means operated in response to said movable means moving said second named permanent magnet to its operative position to interpose a directional magnetic force into the field of the first named permanent magnet to cause said movable element to move to its predetermined position aforesaid.

4. In an electrical indicating instrument having a rotatable indicating element cooperating with a fixed indicating element for indicating the magnitude of a condition and means including a permanent magnet rotatable coaxially with said movable element and a plurality of coils magnetically associated therewith and arranged to be activated and deactivated by flow and cessation of current through said coils and effective when activated for controlling the position of said movable element to indicate said magnitude, apparatus for moving said movable element to a predetermined off-scale position to indicate that the instrument is not operating, comprising a pivotally mounted arm having a permanent magnet secured thereto at its free end movable by the pivotal movement of said arm between an operative position wherein the second named permanent magnet is within the field of the first named permanent magnet but axially offset therefrom and an inoperative position wherein the second named permanent magnet is substantially laterally outside the field of the first named permanent magnet, whereby at the inoperative position said second named permanent magnet. is} electrically;." and mechanically separat'eiand' distinct frcmthee first named-ii-permanent magnet: and-thecoils; ass

consequent operation of the: instrument is in-;. dependenteof said secondnamedspermanent mage net; anelectromagnetic holding: means having a,

wising: respectively: associated in. the circuit witn each: oi said coils for holding: said arm and;v

ed permanent magnet, and resilientimeans;

e -c i e---upon--thede-energizatiomof saidaelectro-a magnetic holding means by. theicessation ofs'curei rent flow :thr-ough all the windings thereof:- for; moving said second named permanent magnatev to its operative position upon cessation of cur rent fiow through all said coils, said two named permanent magnets reacting together when the second named permanent magnet is at its operative position to effect rotation of said rotatable element to said predetermined off-scale position.

5. In an electrical indicating instrument of the ratiometer type having a rotatable indicating element cooperating with a fixed indicating element for indicating the magnitude of a condition and including a permanent magnet mounted for coaxial rotation with said rotatable element and three Y-connected fixed coils magnetically associated with said permanent magnet for controiling the position thereof during periods of current flow through said coils, apparatus for moving said rotatable element to a predetermined 03 608116 position to indicate cessation of current through said coils, comprising a second permanent magnet constructed and arranged for movement between an operative position axially offset from but in the magnetic field of the first named permanent magnet and an inoperative position wherein the second named permanent magnet is substantially laterally outside the field the first named permanent magnet, whereby said second named permanent magnet when at its inoperative position is electrically and mechanically separate and distinct from the magnetic field of said first named permanent magnet and said coils, and whereby the position of said rotatable element and the first named permanent magnet is independent of said second named permanent magnet at the inoperative position of the latter, an electromagnetic holding means having a winding in circuit with each of said coils respectively so that current flow through any one of said coils will result in current fiow through the respectively associated windings of said electromagnetic holding means, said windings being further constructed and arranged so that energization of any one of the windings thereof will be effective to hold said second named permanent magnet at its inoperative position, and resilient means effective upon the de-energization of all said windings of said electromagnetic holding means to move said second named permanent magnet to its operative position, said two named permanent magnets conjointly interacting when the second named permanent magnet is at its operative position to cause a movement of said rotatable element to said predetermined off-scale position.

6. In a ratiometer type indicating instrument having a transversely magnetized rotor and a plurality of deflecting coils adapted upon enered therewith whereby the position. 0t: cvableelement. during. the activation and;

giz'ation to control the position of said rotor, a reset means efiective to move said rotor to a Predetermined position, solely during deenergization of said deflecting coils, comprising a permanent magnet, means mounting said permanent magnet so that it is movable into and substantially away'from a position in the magnetic field of said magnetized rotor, means resiliently urging said permanent magnet toward its position in said field, and means energized concomitantly with said deflecting coils for holding said permanent magnet in its position remote from said field.

'7. Reset means for a ratiometer-type instrument in accordance with claim 6, wherein said concomitantly energized means comprises an electromagnetic holding means having at least one winding in series with one of said deflecting coils.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STA'IES PATENTS Number Name Date 2,382,295 Conrad Aug. 14, 1945 2,382,315 Hiller Aug. 14, 1945 

